# US 10,118,405 B2 · Cross-talk effect in a laser diode array > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,118,405 B2 - Document ID: US10118405B2 - Status: Granted - Kind: B2 - Application number: 15/545,976 - Filed: 2015-04-29 - Published: 2018-01-18 - Granted: 2018-11-06 - Earliest claimed: 2015-04-29 - Assignees: HP Indigo B.V. - Applicants: Hewlett-Packard Indigo B.V. - Inventors: Oron Ambar; Yuval Yunger; Haim Vladomirski - Web page: https://patentgrep.com/patent/US10118405B2 ## CPC - B41J 2/455: using laser arrays {, the laser array being smaller than the medium to be recorded} - B41J 2/45: using light-emitting diode {[LED] or laser} arrays - B41J 29/393: Devices for controlling or analysing the entire machine {; Controlling or analysing mechanical parameters involving printing of test patterns} - G01J 1/4257: {applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam (monitoring arrangements for lasers in general H01S3/0014)} - H04N 1/40031: {for a plurality of reproducing elements simultaneously} - H04N 25/62: Detection or reduction of noise due to excess charges produced by the exposure, e.g. smear, blooming, ghost image, crosstalk or leakage between pixels - B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract An electric cross-talk, ECT, effect of laser-diode array is measured by capturing a first image of a first laser spot of a first laser diode with a second laser diode being turned off (10) and a second image of a second laser spot of the first laser diode while switching on the second laser diode (20). A spot-energy ratio is determined (30) by processing the images, and an ECT-coupling coefficient on the first laser diode is calculated (40) by switching the second laser diode. Compensating for the ECT effect includes determining a signal for predicting the ECT effect on the first laser diode by switching the second laser diode, and generating a driving signal based on a desired current profile and the ECT-prediction signal. ## Claims ### Claim 1 A method for measuring an electric cross-talk (ECT) effect in a laser diode array, wherein the laser diode array comprises a plurality of laser diodes including a first laser diode and a second laser diode; comprising: capturing, by an image sensor, a first image of a first laser spot of the first laser diode with the second laser diode being turned off; capturing, by the image sensor, a second image of a second laser spot of the first laser diode while switching on the second laser diode; determining, by image processing of the first image and the second image, a ratio of laser spot energy of the first laser spot and the second laser spot; and calculating, based on the determined ratio of laser spot energy, an ECT coupling coefficient associated with the ECT effect on the first laser diode by switching the second laser diode. ### Claim 2 (depends on 1) The method according to claim 1, wherein calculating the ECT coupling coefficient is further based on a laser modulation current of the first laser diode, a laser modulation current of the second laser diode and a laser off current of the second laser diode. ### Claim 3 (depends on 1) The method according to claim 1, wherein capturing a first image, capturing a second image, determining a ratio of laser spot energy and calculating an ECT coupling coefficient is performed for each pair of laser diodes in the plurality of laser diodes. ### Claim 4 (depends on 1) The method according to claim 1, wherein the laser diode array is a monolithic laser diode array; wherein the laser diode array and the image sensor are members of a scanning writing head of a liquid electrophotography print press (LEP); and wherein capturing the first image and capturing the second image is performed during a scanning motion of the scanning writing head. ### Claim 5 (depends on 1) The method according to claim 1, wherein capturing the first image and the second image, determining the ratio of laser spot energy and calculating the ECT coupling coefficient is automatically performed by synchronizing a writing head controller switching each of the plurality of laser diodes and the image sensor. ### Claim 6 (depends on 1) The method according to claim 1, further comprising determining an ECT prediction signal for predicting an ECT effect on the first laser diode by switching the second laser diode; and generating, for driving the first laser diode with a desired current profile, a driving signal based on the desired current profile and on the ECT prediction signal. ### Claim 7 A method for compensating for an electric cross-talk, ECT, effect in a laser diode array, wherein the laser diode array comprises a plurality of laser diodes including a first laser diode and a second laser diode; comprising: determining an ECT prediction signal for predicting an ECT effect on the first laser diode by switching the second laser diode; and generating, for driving the first laser diode with a desired current profile, a driving signal based on the desired current profile and on the ECT prediction signal. ### Claim 8 (depends on 7) The method according to claim 7, wherein determining the ECT prediction signal is based on an ECT coupling coefficient associated with the ECT effect on the first laser diode by switching the second laser diode. ### Claim 9 (depends on 8) The method according to claim 8, further comprising: capturing, by an image sensor, a first image of a first laser spot of the first laser diode with the second laser diode being turned off; capturing, by the image sensor, a second image of a second laser spot of the first laser diode while switching on the second laser diode; determining, by image processing of the first image and the second image, a ratio of laser spot energy of the first laser spot and the second laser spot; and calculating the ECT coupling coefficient based on the determined ratio of laser spot energy. ### Claim 10 A writing head for a digital press for transforming a digital image to a physical image on a photoconductor; the writing head comprising: a plurality of laser diodes including a first laser diode and a second laser diode; an image sensor to capture a first image of a first laser spot of the first laser diode with the second laser diode being turned off and capture a second image of a second laser spot of the first laser diode while switching on the second laser diode; a writing head controller comprising a processor and a memory, the memory comprises executable instructions that when executed by the processor cause the writing head controller to determine, by image processing of the first image and the second image, a ratio of laser spot energy of the first laser spot and the second laser spot, and calculate, based on the determined ratio of laser spot energy, an electric cross-talk (ECT) coupling coefficient associated with an ECT effect on the first laser diode by switching the second laser diode. ### Claim 11 (depends on 10) The writing head according to claim 10, wherein the memory further comprises executable instructions that when executed by the processor further cause the writing head controller to determine an ECT prediction signal for predicting an ECT effect on the first laser diode by switching the second laser diode, and generate, for driving the first laser diode with a desired current profile, a driving signal based on the desired current profile and on the ECT prediction signal. ### Claim 12 (depends on 10) The writing head according to claim 10, the image sensor to implement a delay between capturing the first image and the second image. ### Claim 13 (depends on 10) The writing head according to claim 10, the image sensor to capture the second image in response to a trigger voltage or current threshold. ### Claim 14 (depends on 10) The writing head according to claim 10, further comprising a spectral filter on e image sensor. ### Claim 15 (depends on 10) The writing head according to claim 10, the writing head controller to apply a weighting function that models sensitivity or non-linear signal processing of the image sensor. ### Claim 16 (depends on 10) The writing head according to claim 10, wherein the plurality of laser diodes includes an array of laser diodes; and the writing head controller to calculate an ECT coupling coefficient for all combinations of any two laser diodes in the array of laser diodes. ### Claim 17 A writing head for a digital press for transforming a digital image to a physical image on a photoconductor; the writing head comprising: a plurality of laser diodes including a first laser diode and a second laser diode; a writing head controller including a processor and a memory, the memory comprises executable instructions that when executed by the processor cause the writing head controller to determine an electric cross-talk (ECT) prediction signal for predicting an ECT effect on the first laser diode by switching the second laser diode, and generate, for driving the first laser diode with a desired current profile, a driving signal based on the desired current profile and on the ECT prediction signal. ### Claim 18 (depends on 17) The writing head according to claim 17, further comprising an image sensor for capturing a first image of a first laser spot of the first laser diode with the second laser diode being turned off and capturing a second image of a second laser spot of the first laser diode while switching on the second laser diode; wherein the memory further comprises executable instructions that when executed by the processor further cause the writing head controller to determine, by image processing of the first image and the second image, a ratio of laser spot energy of the first laser spot and the second laser spot, and calculate, based on the determined ratio of laser spot energy, an ECT coupling coefficient associated with the ECT effect on the first laser diode by switching the second laser diode. ### Claim 19 A writing head for a digital press for transforming a digital image to a physical image on a photoconductor; the writing head comprising: a plurality of laser diodes including a first laser diode and a second laser diode; a writing head controller comprising an electronic hardware circuit with interconnected logic gates, the electronic hardware circuit, when powered, causes the writing head controller to determine an electric cross-talk (ECT) prediction signal for predicting an ECT effect on the first laser diode by switching the second laser diode, and generate, for driving the first laser diode with a desired current profile, a driving signal based on the desired current profile and on the ECT prediction signal. ### Claim 20 (depends on 19) The writing head according to claim 19, further comprising an image sensor for capturing a first image of a first laser spot of the first laser diode with the second laser diode being turned off and capturing a second image of a second laser spot of the first laser diode while switching on the second laser diode; wherein the writing head further comprises a writing head controller comprising an electronic hardware circuit with interconnected logic gates, the electronic hardware circuit, when powered, causes the writing head controller to determine, by image processing of the first image and the second image, a ratio of laser spot energy of the first laser spot and the second laser spot, and calculate, based on the determined ratio of laser spot energy, an ECT coupling coefficient associated with the ECT effect on the first laser diode by switching the second laser diode.